Many leaders of the American Revolution welcomed the idea that their new nation would grow up to be an empire. To them, the concept was compatible with a republic; it meant size and benign influence. David Ramsay, South Carolina's delegate to the Continental Congress, wrote as early as 1778 that the grandeur of the American continent provided the basis for a realm that would make "the Macedonian, the Roman, and the British sink into insignificance." George Washington thought of the new country as a "rising" or an "infant" empire. Thomas Jefferson, who secured the vast Mississippi and Missouri valley corridors, famously envisaged an "empire of liberty." But whose liberty? The idea of empire as conquest or subjugation was curiously absent from this postindependence reverie. Cheered by the euphemism of "manifest destiny" deep into the nineteenth century, Americans of European origin continued to enjoy the incredible lightness of empire.

Subsequent observers would contend that the process of building and managing an empire is often violent, unfettered by concerns about law and equality. Empire, as Joseph Conrad wrote and American anti-imperialists came to acknowledge, had a heart of darkness. As Jane Burbank and Frederick Cooper, the authors of the massive comparative study Empires in World History, argue, "Terror was the hidden face of empire." And it has not always been so hidden, either.

The word "imperium" originally signified the authority delegated by the Senate of the Roman Republic to exercise command over the republic's own citizens and subdue others. It came to be applied to Rome's new territories throughout Italy and then beyond, even before Augustus founded the Principate, the first formal phase of the Roman Empire proper. More recently, in the United States, the growth of presidential power has periodically awakened concerns about what the historian Arthur Schlesinger, Jr., termed "the imperial presidency," that is, the growth of executive authority at the expense of legislative supervision and public dissent.